Use of artificial intelligence techniques, especially the recent focus on formal representation of the knowledge of experts, is the latest and most promising of applications of the computer to medicine. It is already clear that the techniques are powerful and that the proof-of-concept and feasibility phases of medical applications have been successfully passed. This technique has been shown feasible in the areas of infectious disease, glaucoma management, patient present illiness, and in the general differential diagnosis in internal medicine. The proposed program focuses on fundamental research in biomedical knowledge representation for use by computers. The program is a coordinated effort of the individual projects plus core research - each concentrating on different aspects of the main theme of using biomedical knowledge, stored symbolically, in computer programs that can reason about and explain solutions to medical and biomedical problems.